1. Field of the Invention
The present invention relates to suitcases and other heavy luggage cases, and, more particularly, to suitcases which are equipped with built-in casters on which they can be wheeled from place to place.
2. Description of the Prior Art
Suitcases of average or larger than average dimensions, when fully packed, may be so heavy that the user is faced with considerable strain and fatigue, if he is to carry one, or maybe even two of them from his residence to his means of transportation, or vice versa, or from one means of transportation to another at a transfer station.
This problem has already led to the development of suitcases which have casters arranged in pairs on the lower longitudinal side, opposite the carrying handle of the suitcase, or near the corner between the lower longitudinal side and one of the two transverse sides. To the extent that only one pair of casters is used, the caster wheels need not be swivelable for a change in direction. Where two caster pairs are arranged on the lower longitudinal side of the suitcase, one or both pairs of casters have caster wheels that are swivelable about a vertical axis.
Suitcases with a single pair of casters at a bottom corner are in most cases equipped with an auxiliary carrying handle or guide handle at the opposite corner. This handle may be of the type which is extendable and retractable or pivotably attached to the suitcase. The user of such a suitcase has to lift it on one side with the aid of the auxiliary handle, thereby carrying a portion of the weight of the suitcase himself. In contrast, when the suitcase is equipped with four caster wheels, its entire weight is carried by the wheels, and the suitcase is displaced by pulling on its carrying handle, in a stooped posture, or by pulling on a special pull strap attached to the case. The caster assemblies are in most cases rigidly mounted on the outside of the frame of the suitcase. In this mounting arrangement, even caster assemblies with very small wheels will protrude by their full height over the outline of the suitcase frame, with the resultant risk that, when the suitcase encounters a doorstep or a depression in the floor, its caster wheels become caught and damaged, or even torn off, thereby frequently also causing damage to the suitcase frame itself. This disadvantage is also present, when such a suitcase is handled in a check room or when it is placed on a luggage cart or into a container, where it may have to be pushed onto a ledge or on top of other luggage pieces and later pulled off again.
In a known caster arrangement, disclosed in U.S. Pat. No. 3,948,365, the above-mentioned difficulties are largely avoided, inasmuch as a non-swivelable caster wheel is rotatably supported in a plastic housing which forms a recess for the caster wheel, so that the housing partially encloses the caster wheel in a hood-like fashion from the side opposite its contact point with the floor. The recess of the housing is surrounded by a flange-like collar and is shaped to match the curvature of the rounded corner portion of the suitcase between the lower longitudinal side and one of its two transverse sides. In this corner area, the suitcase frame has two openings arranged side-by-side into which the hood-shaped caster housings are inserted in such a way that their flange-like collars abut against the outer side of the suitcase frame. The collars of the housings are permanently attached to the suitcase frame, using rivet fasteners, for example, near the two longitudinal extremities of the housing collar. The fact that these caster wheels have a comparatively large diameter, on the one hand, and are to a large extent recessed into the suitcase frame, on the other hand, results in a comparatively shallow rise of the peripheral surface of the caster wheels from the longitudinal side and from the transverse side of the suitcase.
Up to the present, however, such an advantageous configuration has only been obtained in the corner area of the suitcase, where the latter has a single pair of non-swivelable casters. The suitcase needs to be tilted upwardly, in order to become steerable. On any other point of the suitcase contour, the space requirements for similar caster assemblies, which would then have to consist of two caster pairs, would be too large. Furthermore, the mere provision of two pairs of casters would not provide the required steerability, unless at least one pair of casters is swiveled. The limitation to one caster pair at the corner of the suitcase means, on the other hand, that the user of such a suitcase will have to carry a significant portion of the weight of the suitcase himself.
From French Pat. No. 72 18 946 is known an arrangement of caster assemblies where each assembly has a swivelable caster wheel which is rotatably supported in a bearing bracket. The latter is attached to the bottom of a recessed caster housing by means of a swivel bearing. Like conventional exposed swivel casters, these caster wheels are free to swivel over 360.degree.. They therefore require a caster housing with a recess of a size that will limit its use to the closed longitudinal side of travel trunks of a certain minimal size, given the necessity of the swivelable caster wheels not to be smaller than a predetermined diameter below which they would not be suitable for the intended application. For conventional hand-carried suitcases, especially cases of the type which have approximately identical cover and bottom shells opening along a central plane, these caster assemblies are not suitable, because they would require such large openings in the suitcase frame for the caster housings that the strength and rigidity of the frame would no longer be adequate.